Armor panel

ABSTRACT

An armor panel for ballistic protection, comprising at least an armor layer which is at least partially made of cemented carbide in the form of metal-carbide aggregate embedded within a metal binder matrix.

FIELD OF THE INVENTION

This invention relates to armor panels, in particularly composite armorpanels comprising one or more protective layers.

BACKGROUND OF THE INVENTION

A standard armor panel of the kind to which the present inventionparticularly refers, comprises a multitude of layers, designed togradually absorb the kinetic energy of the impact, delivered to thepanel by an incoming projectile and finally to completely avoidpenetration of the projectile or its fragments to the body to beprotected.

The layers used in such armor panels may be divided into two groups:hard layers, e.g. steel or ceramic, and soft layers, e.g. Aramid or UHMWHDPE (Ultra High Molecular Weight High Density PolyEthylene). The harderlayers are usually positioned facing the expected threat and absorb mostof its kinetic energy thereof, thereby slowing it down and shatteringand/or deforming it substantially. The softer layers absorb the remainsof the kinetic energy of the projectile, stopping it and its fragments,thereby preventing them from deforming/coming in contact with the bodyto be protected or at least from penetrating it.

It is known in the art to use armor panels having several hard layers ofdifferent materials in order to better absorb the kinetic energy of theincoming projectile.

The choice between various materials that may constitute the hard and/orsoft layers of the armor panel is affected by the required endproperties of the panel, such as ballistic properties, weight, etc.Thus, for example, a hard ceramic layer may be light-weight, yetbrittle, while a hard steel layer having similar ballistic properties,may be very heavy, though easy to work with.

SUMMARY OF THE INVENTION

According to the present invention, there is provided an armor panel forprotecting a body from an incoming projectile having an expected impactdirection, said armor panel comprising at least an armor layer made ofcemented carbide in the form of metal-carbide aggregate embedded withina metal binder matrix.

The armor panel may be adapted to protect the human body, i.e. be in theform of personal armor such as a vest, or alternatively, be designed toprotect a structure, mobile or immobile, adapted to house individuals tobe protected, e.g. a vehicle.

The ‘metal-carbide aggregate’ should be understood as being in the formof granular/powder material, and ‘embedded within a metal binder matrix’should be understood as being homogenously spread throughout the metalbinder matrix.

It should be noted that cemented carbide may be divided into two majorgroups, a first group in which the cemented carbide comprises a carbideaggregate embedded within a binder matrix, and a second group in whichthe cemented carbide comprises an aggregate without a binder.

For the purpose of simplicity, the metal of said metal-carbide will bereferred herein as ‘carbide metal’ and the metal used for said metalbinder matrix will be referred herein as ‘binder metal’.

Said carbide metal and said binder metal may differ in their inherentcharacteristics. More particularly, the properties of said carbide andsaid binder metal may differ from one another. The metal of said carbidemetal may be chosen from a group of refractory metals, in order toprovide said cemented carbide with high hardness, high fracturetoughness and a high melting point. The metal of the binder metal may bea metal having a lower hardness than that of the metal of themetal-carbide, in order to reduce the brittleness of the cementedcarbide and provide it with high fracture toughness.

Cemented carbide may be manufactured by a variety of processes in solid,liquid and vapor phases as known per se, for example hot isostaticpressing (HIP) or sintering. During manufacture, binder metal andcarbide are heated up until the binder metal is melted down while theaggregate remains in solid phase, thereby providing the cemented carbidewith its desired morphology. This is due to the carbide having a highermelting point than that of the binder metal.

The carbide metals are so chosen as to provide the metal-carbide withrelatively high density, high toughness and hardness. Thus, themetal-carbides described above may have a density ranging from 4.93÷15.8gr/cc, a toughness ranging from 240÷550 MPa, hardness ranging from1400÷3000 HV50and a melting point ranging from 1800÷3990° C. Fracturetoughness of the above metal-carbides is relatively not high, e.g. up toabout 12 Mpa*(m^(1/2)), Some examples of such metal-carbides may be WC,TiC, TaC, NbC, ZrC, HfC, VC, Cr3C2, Mo2C etc. The cemented carbide maycomprise several carbide metals forming several kinds of aggregateswhile using the same metal binder. Some examples of such cementedcarbides may be WC—Co, WC—TiC—TaC—NbC—Co, WC—Cr3C2—Co,WC—TiC—TaC—NbC—Cr3C2—Co, TiCN—WC—TiC—TaC—NbC—Ni—Co—Mo2C—VC.

Said binder metal may have a density ranging from 7.8÷8.9 gr/cc,fracture toughness ranging up to 400 Mpa*(m^(1/2)) which is considerablyhigher than that of the metal-carbides, and a melting point ranging from1450÷1536° C. Some examples of such binder metals may be Co, Ni, Fe etc.

The binder metals listed above have an atomic weight essentially lowerthan that of the carbide metals, providing the cemented carbide used forthe armor panel with an essentially lower overall density than a similarcemented carbide in which the metal (such as W, Ti, Nb etc.) is of anatomic weight close to that of the carbide metals.

In the cemented carbide layer, the metal-carbide aggregate may be in theform of grains homogenously spread throughout the binder. The grain sizeof the metal-carbide aggregate may be such that it does not exceed 20 μmper grain. For example, for grains of tungsten carbide (WC), the grainsize may range between about 0.5 μm÷2.3 μm, more particularly between0.7 μm÷2.1 μm, and still more particularly between 0.9 μm÷1.9 μm, andhaving an average grain size of about 1.3 μm. For grains of titaniumcarbide (TiC), the grain size may range between about 2.5 μm÷6.2 μm,more particularly between 2.7 μm÷6 μm, and still more particularlybetween 2.9 μm÷5.8 μm, and having an average grain size of about 2.7 μm.

The composition of the cemented carbide may be such that, by weightpercentage, the metal carbide aggregate does not exceed 80%. The metalcarbide aggregate may constitute between about 80÷96%, more particularlybetween about 85÷94%, and still more particularly between about 90÷92%.The metal binder matrix may be such that, by weight, does not exceed80%. The metal binder matrix may constitute between about 4%÷20%, moreparticularly between about 6%÷15%, and still more particularly betweenabout 8%÷10%.

The composition of the cemented carbide may also be such that, by volumepercentage, the metal carbide aggregate does not exceed 70%. The metalcarbide aggregate may constitute between about 82÷96%, more particularlybetween about 86÷92%, and still more particularly between about 88÷90%.The metal binder matrix may be such that, by volume, does not exceed30%. The metal binder matrix may constitute between about 4%÷18%, moreparticularly between about 8%÷14%, and still more particularly betweenabout 10%÷12%.

It should be appreciated that the cemented carbide may comprise metalcarbide aggregates of various metal, for example both titanium carbide(TiC) aggregates and tungsten carbide (WC) aggregates. In this case, thecomposition of the cemented carbide may be such that, by weight, WCranges between 70%÷85%, more particularly between 74%÷80%, and stillmore particularly between 76%÷79%. The weight percentage of the titaniumcarbide (TiC) may range between 10%÷20%, more particularly between12%÷18%, and still more particularly between 14%÷16%. The weightpercentage of the binder may range between 4%÷20%, more particularlybetween 6%÷15%, and still more particularly between 8%÷10%.

In the above case, the composition of the cemented carbide may be suchthat, by volume, WC may range between 50%÷65%, more particularly between53%÷62%, and still more particularly between 56%÷60%. The volumepercentage of the titanium carbide (TiC) may range between 24%÷40%, moreparticularly between 27%÷36%, and still more particularly between30%÷33%. The volume percentage of the binder may range between 4%÷16%,more particularly between 6%÷14%, and still more particularly between9%÷12%.

The said cemented carbide may have an overall density ranging from5.5÷15.5 gr/cc, a toughness ranging from 1.7÷4.1 GPa, hardness rangingfrom 87÷93 HRa, and fracture toughness up to 20 Mpa*(m^(1/2)), i.e.lower than that of the binder metal yet higher that of themetal-carbide.

It should also be understood that the above compositions are chosenspecifically in order to provide the cemented carbide, on the one hand,with high hardness due to the metal-carbide aggregate, and on the otherhand, high fracture toughness due to the metal-binder matrix. Inparticular, since the cemented carbide is used in an armor panel, thecomposition is chosen such that it may be adapted to withstand a highimpact during a short time interval.

It should be noted that the armor panel may also comprise a layer whichis partially made of cemented carbide, for example, containing cementedcarbide pellets and/or tiles. The term ‘pellets’ should be understood torefer to armor elements adapted to be incorporated within the armorpanel, and usually having a polygonal/cylindrical shape extending alonga central axis. The design of the armor panel may be such that thepellets/tiles are incorporated within a matrix which is of differentcharacteristics than that of the metal-binder matrix, for example, madeof a light weight metal (e.g. aluminum) or a thermoplastic/thermoseticpolymer (e.g. resin).

One of surprising properties that may be obtained in the cementedcarbide armor layer as defined above, is that this layer, on the onehand, exhibits uniform mechanical properties as in known, and widelyused in the field of armor, ceramic tiles, and on the other hand, may beessentially less brittle then these tiles (due to the inherent ductileproperties of the binder metal), due to which the armor layer may have ahigh multi-hit capability compatible to that of an armor layer made ofmetal carbide pellets or armor elements within a matrix, and the abilityto be processed, in particular cut, without causing its fracture, e.g.using CNC tools, to have a desired design.

Tests carried out on an armor panel having an armor layer of cementedcarbide as described above, in comparison with a reference armor panelhaving a steel armor layer of a greater thickness than that of thecemented carbide layer and otherwise being of a design similar to thatof the cemented carbide panel, exhibits penetration resistanceproperties similar to that of the reference panel, though at anessentially lower weight. The armor panel may comprise two or morelayers which may be made of the same or different cemented carbides.

Said armor panel may comprise in addition to the at least one layer ofcemented carbide, a complementary armor layer positioned in front orbehind said cemented carbide layer, and/or an optional a backing layer.The additional layers may be made of any appropriate ballisticmaterials, such as steel, metal, ceramic or any other ballisticmaterial.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carriedout in practice, embodiments will now be described, by way ofnon-limiting examples only, with reference to the accompanying drawings,in which:

FIG. 1 is a schematic cross-sectional view of a conventional, referencearmor panel;

FIG. 2A is a schematic cross-sectional view of an armor panel accordingto one embodiment of the present invention;

FIGS. 2B and 2C are respective schematic morphological representationsof a cemented carbide according to the present invention and a hardmetal according to the prior art;

FIG. 3 is a schematic cross-sectional view of an armor panel accordingto another embodiment of the present invention;

FIG. 4 is a schematic cross-sectional view of an armor panel accordingto yet another embodiment of the present invention;

FIG. 5 is a schematic cross-sectional view of an armor panel accordingto still a further embodiment of the present invention; and

DETAILED DESCRIPTION OF EMBODIMENTS

In embodiments described below, examples of different designs of anarmor panel according to the present invention are presented, includinga cemented carbide layer either alone or with additional layers.Examples of materials and processes that may be used for the manufactureof the cemented carbide layer are generally presented in the Summary ofInvention, whilst for the purpose of the present detailed description,one specific non-limiting example of the cemented carbide will bereferred to, which is a cemented carbide produced from tungsten carbideas a metal-carbide aggregate with cobalt as a binder metal, by a processincluding heating up both the binder metal and the carbide to hightemperatures of about 1600° C. Since the melting point of the carbide,in this case tungsten-carbide (≅1800° C.), is higher than that of thecobalt binder (≅1550° C.), the cobalt binder is melted to assume aliquid phase while the tungsten-carbide aggregate remains in solidstate. This manufacturing process provides even dispersion of theaggregate within the binder and causes the resulting cemented carbide tohave extremely low porosity, e.g. about 2%.

FIG. 2B shows morphological representation of a cemented carbide of thekind used in armor panels according to the present invention, inparticular such as in the specific example described above. As seen inFIG. 2B, the carbide metal aggregate 42 is formed in clusters (shown ingray) and is bound by a binder 44 (shown in white). The clusters 42 areimmersed in the binder 44, i.e. the connection of the clusters 42 to thebinder 44 is achieved by the clusters 42 being a kind of dissolved in,and homogenously spread throughout, the metal binder 44.

FIG. 2C shows a cemented carbide of a different kind where no metalbinder matrix is used. Thus, the cemented carbide shown in FIG. 2Ccomprises WC clusters 52 (gray), TiC clusters 54 (dark gray), and TaCclusters 56 (light gray). In the present example, there is no binderbetween the clusters, and they are attached directly to one another insolid phase.

In the example shown in FIG. 2B, the presence of the binder provides thematerial with fracture toughness of up to 20 Mpa*(m^(1/2)), as opposedto about 12 Mpa*(m^(1/2)) of the material shown in FIG. 2C. Increasedfracture toughness may allow for a higher multi-hit capability of thearmor panel.

For the purpose of illustrating the performance of armor panelsdescribed below, they will be compared with that of a reference armorpanel RP (shown FIG. 1), made of steel and having a thickness T, and aweight W, as summarized in the table below:

Sample Properties No. Areal Weight [Kg/m²] Thickness [mm] 1 172.5 22

With reference to FIG. 2, first example of an armor panel according tothe present invention, generally designated as 1, is shown, made of amonolith layer 10 of the cemented carbide, constituted by a metal bindermatrix 12 and a carbide aggregate 14.

To compare the ballistic performance of the armor panel 1 with that ofthe above reference panel RP, the armor panel 1 has been produced with athickness t of 10 mm and an areal weight w approx. 69 Kg/m². Namely, thearmor panel 1 is essentially lighter and thinner than the referencearmor panel RP, the respective weight and thickness ratios m and dbetween the armor panels 2 and 1 being

${m = {\frac{w}{W} = {\frac{69}{172} = 0.401}}},\mspace{14mu} {{{and}\mspace{14mu} d} = {\frac{t}{T} = {\frac{10}{22} = {0.454.}}}}$

Surprisingly, despite the above essential thickness and weight ratios dand m, respectively, the armor panel 1 has appeared to provide the samelevel of protection (level 3 threats according to STANAG 4569), as thatof the armor panel 1 and withstand AP rounds and FSP. It should also beappreciated that the armor panel 1 may provide protection against hollowcharges as well.

Turning now to FIG. 3, another example of an armor panel is shown,generally designated as 1′. The armor panel 1′ comprises a first layer10 of the cemented carbide and a second layer 20 of steel, and suchcombination appears to improve anti-penetration ability of the entirearmor panel.

It should be noted that the terms ‘first’ and ‘second’ are used withreference to an expected impact direction of incoming projectiles, i.e.among the two layer the ‘first’ layer meets an incoming projectilebefore the ‘second’ layer. Hereinafter, arrow 100 denotes the expectedimpact direction.

The panel 1′ may for example, be produced with a thickness t′ of thefirst, cemented carbide layer 10 being 4 mm and a thickness T′ of thesecond, steel layer 20 being 5 mm. Such an armor panel 1′ has appearedto withstand the same threats as those withstood by the reference armorpanel 1, whilst being essentially thinner and lighter.

With reference to FIG. 4, a further example of an armor panel is showngenerally designated as 1″. The armor panel 1″ comprises a first layer10 of the cemented carbide and a second layer 30 made of a plurality ofHDPE sheets. The panel 1″ may, for example, be produced with a thicknesst″ of the first, cemented carbide layer 10 being 4 mm, and a thicknessT′ of the second, HDPE layer 30 being 23 mm. Such an armor panel 1″ hasalso been shown to withstand the same threats as those withstood by thereference armor panel 1, though being essentially lighter.

Turning now to FIG. 5, a still further example of an armor panel isshown, generally designated as 1′″. The armor panel 1″ comprises a firstlayer 10 of cemented carbide, a second layer 20 of steel, and a third,backing layer 30 made of a plurality of Kevlar® sheets. Several testshave been performed on panels having this design, though differentthicknesses and different weights, and their results are presentedbelow:

Sample Properties No. Areal Weight [Kg/m²] Thickness [mm] 1 86.3 18.5Exp. No. Bullet Type Velocity [m/s] Penetration 1 7,62*51 AP 952 No (WCcore) 2 7.62*51 AP 933 No (WC core) 3 7.62*51 AP 949 No (WC core) 47.62*51 AP 950 No (WC core) 5 7.62*51 AP 948 No (WC core) 6 7.62*51 AP942 No (WC core) 7 7,62*51 AP 950 No (WC core) 8 7.62*51 AP 945 No (WCcore) Sample Properties No. Areal Weight [Kg/m²] Thickness [mm] 2 98.7422.8 Exp. No. Bullet Type Velocity [m/s] Penetration 1 20 mm FSP 788 No2 20 mm FSP 774 No 3 20 mm FSP 815 No Sample Properties No. Areal Weight[Kg/m²] Thickness [mm] 2 90.2 9.1 Exp. No. Bullet Type Velocity [m/s]Penetration 1 20 mm FSP 789 No 2 20 mm FSP 795 No Sample Properties No.Areal Weight [Kg/m²] Thickness [mm] 4 94.8 18.2 Exp. No. Bullet TypeVelocity [m/s] Penetration 1 20 mm FSP 845 No 2 20 mm FSP 794 NoProperties 5 Areal Weight [Kg/m²] Thickness [mm] 5 90.2 19.1 Exp. No.Bullet Type Velocity [m/s] Penetration 1 7.62 × 54 AP B32 862 No 2 7.62× 54 AP B32 850 No 3 7.62 × 54 AP B32 847 No 4 7.62 × 54 AP B32 734 No 57.62 × 54 AP B32 738 No 6 7.62 × 54 AP B32 735 No 7 7,62 × 54 AP B32 864No 8 7.62 × 54 AP B32 860 No

It should be obvious from the above test tables that the armor panelaccording to the present invention is capable to provide at least thesame ballistic protection as the reference armor panel RP, however, withreduced overall weight and thickness.

Those skilled in the art to which this invention pertains will readilyappreciate that numerous changes, variations, and modifications can bemade without departing from the scope of the invention.

1. An armor panel for ballistic protection, comprising at least an armorlayer which is at least partially made of cemented carbide in the formof metal-carbide aggregate embedded within a metal binder matrix.
 2. Anarmor panel according to claim 1, wherein the metal-carbide aggregate isin the form of grains having a grain size not exceeding 20 μm.
 3. Anarmor panel according to claim 1, wherein the composition is such thatsaid metal-carbide aggregate constitutes at least one of the following:(i) at least 70% by volume; and (ii) at least 80% by weight.
 4. An armorpanel according to claim 1, wherein the composition is such that saidmetal binder matrix constitutes at least one of the following: (i) Nomore than 30% by volume; and (ii) No more than 80% by weight.
 5. Anarmor panel according to claim 1, wherein said carbide aggregate has amelting point ranging from 1800÷3990° C.
 6. An armor panel according toclaim 1, wherein the metal of said metal binder has a melting pointranging between 1450÷1536° C.
 7. An armor panel according to claim 1,wherein said cemented carbide has a fracture toughness ranging from 7÷20Mpa*(m^(1/2)).
 8. An armor panel according to claim 1, wherein saidcemented carbide has a hardness ranging from 87÷93 HRa.
 9. An armorpanel according to claim 1, wherein said cemented carbide has a densityranging from 5.5÷15.5 gr/cc.
 10. An armor panel according to claim 1,wherein said cemented carbide has a porosity ranging from 0÷2%.
 11. Anarmor panel according to claim 1, wherein said metal-carbide aggregatehas a higher melting point than that of said metal binder.
 12. An armorpanel according to claim 1, wherein said metal-carbide aggregate has alower fracture toughness than that of said metal binder.
 13. An armorpanel according to claim 1, wherein said armor layer is a singlecemented carbide monolith.
 14. An armor panel according to claim 1,wherein said armor layer comprises a plurality of cemented carbidepellets.
 15. An armor layer for use in ballistic armor made of cementedcarbide in the form of a metal-carbide aggregate embedded within a metalmatrix, wherein the metal of said metal-carbide is a refractory metal.16. A method of manufacture of an armor panel, including manufacture ofan armor layer at least partially made of cemented carbide in the formof a metal-carbide aggregate embedded within a metal matrix, andincorporating said armor layer within said armor panel.